Carrier relaying



.March 20, 1945.

s. L. GoLDsBoRoUGl-l 2,372,078

CARRIER RELAYING Filed Dec. s, 1942 5 l D zzp ,ee/75 U 76 L @j 4a D., [oz 79 ,ze 77 L S6- n @y "4 63 csp C56 WITN ESSES:

INVENTOR BYQMMA ATTOR N EY Patented Mar. 20, 1945 yUNITED STATES PATENT OFFICE CARRIER RELAYIN G Shirley L. Goldsborough, BaskingRidge, N. J., assignor to Westinghouse Electric & Manufacturing Company, vEast Pittsburgh`,`Pa.,` a corporation of Pennsylvania Application December s, 1942, serial N0. 468,229

2 Claims. (Cl, 1775-1294) My invention relates to carrier-supervised protective relaying systems for protecting transmission linesv against faults, and it has` particular relation to the provision of means for making it possible to utilize the carrier'with a desensitized receiver, for purposes other vthan fault-protection, as in the detection of sleet on the transmission wires, without impairing the full sensitivity and operativeness of the receiver for the proper coordination of the fault-detection, inthe event that a fault shouldoccur during. the desensitizedoperation of the carrier-current equipment.

The object of my invention v`is to provide a system whereby the results just mentioned may be accomplished.

lAn exemplary form of embodimentiof my invention is shown in the drawing, wherein'Fig. 1 is a schematic diagram of the direct-current connections, showing a simplified apparatus forfillustrating the application of my invention, and Fig. 2 is a Wiring diagram showingthe'alternatingcurrent connections as Well as the direct-current connections.

In Fig. 2, I have illustrated my'inventionas being applied to the protection of one end of .a

, three-phase transmission-line section 3,:the:three phase-conductors being distinguished by the-letters A, B and C. The line-section 3 is connected, through a circuit breaker 4, lto a( bus 5,- which/is energized, through delta-star step-up' transformers 6, from a generator-bus or supplyeline 1.

Various line-responsive relays are provided,

lwhich are supplied with energy.' by means of .a

-will be subsequently described.

`The circuit breaker 4 is provided'with a `tripcol TC, which is energized, in accordance `with the protective relay Ameans (subsequently described), through an auxiliary breaker-switch 4a, and a direct-current sourcey which .is .sym-

of phase-fault impedance-relays in each phase,

-V said relays beinglof4 increasing sensitivities corresponding to what is known as first-zone, secondr-zone and third-zone operation, the different zones being indicated by the numerals I, 2 and 3,.y and the diierent phases being distinguishedbythe letters A, B, and C. As this type ofrelaying-system is well known, it has not been bolized by the battery-terminals and `My invention is illustrated as being applied to .a relaying. system of a type. utilizing, anumber shown in its entirety, but I have selected the second and third-zone impedancerelays of phase-A .to illustrate my inventionpas indicated at ZZA and 23A. Each impedance-'relay element consists-of a, voltage-responsive restraining-coil I2 .and a current-responsive operating-coil I3, suitably energized, in-any desired'manner, so that the relay is responsive to the line-impedance,

The illustrated relaying-system also Autilizes phase fault responsive directional elements, which are represented by thephase-A directional element DA, a residual-current directional element D0,l and a, number of ground-fault detector-elements of different sensitivities, represented .by the .elements 102'v and 103, the latter being the more sensitive.

Each of thev relaying elements Z2A, Z3A, DA, D0, 102 and I03 has a single makecontact, which is sufliciently identified by designating vit with the corresponding relay-designa- ,.ticn such as ZZA, etc.

The particular energizing-connections for these relays, as illustrated in Fig. 2, include `the enerfgization. of the Z3A operating-coil I3 in response tothe line-current IA, said coil being-interposed -between the phase-A line-current transformer 8 and a'neutral conductor I5. Auxiliary relaying apparatus, symbolically indicated at I4 and I4',

is energized responsively to the two other line- 4 currents, and also connected to the neutral-conjductor I5, so that the residual or zero-phasesequence currents flow through this neutral conductor, and are then supplied to the three groundfault relays 103, 102 `and D0, the circuit being completed with the neutral conductor I6 of the Vstar-connected line-current transformers 8. The

polarizing winding of the ground-directional element D0 is illustrated as being energized from the grounded-neutral transformer I I.

The operating coil I3 0f the ZZA relay, and the .directional-winding terminals of the phasedirectional relay DA, are shown as being energized re- .sponsively to the delta-current (IA-IB), supplied from the auxiliary transformers S, in a circuit including other relaying equipment which has been symbolized at I'I, and terminating with a star-point connection lil. The other two delta currents .are supplied to the star-point I8,

through other relaying equipment symbolized at i9 and i3'. While one particular type of relayenergization, and relay-response, has been illustrated, it is to be understood that my invention is not limited to the precise type of relay.

The relaying system also includes a carriercurrent transmitter 2|, which comprises an oscillator-tube 22, illustrated as comprising a cathode 23, a grid 24, a screen 25, and an anode or plate 2G. The cathode 23' is connected to a cathode-circuit 21 which is adapted to be connected to the negative battery-terminal through the fault-responsive relaying equipment, the circuits of which will be subsequently described. The I anode 25 is connected to a plate-circuit 28 which is connected, through a high-frequency chokecoil 29, to a source of positive potential, indicated a's being a tap 38 on a potentiometer 3l which is energized across the battery-terminals (-i-l and The oscillator-tube 22 is caused to oscillate at a predetermined radio or carrier-current frequency by means of a tuned circuit 32 which is illustrated as comprising a, variometer 33 and three capacitors 34, 35 and 38. One terminal of the variometer 33 is connected, through a, blocking-capacitor 31, to the -plate-circuit 28. The

other terminal of the variometer 33 is connected,A

at es, to the grid 24, the grid being also con-y f nected to the cathode-circuit 21 through a gridleak resistor 33. The screen 25 is connected to the positive terminal through a conductor 40.

The cathode-circuit 21 of the oscillator is connected to the mid-point between the two capaci tors and 36 ofthe tuned oscillator-circuit 32, these capacitors being matched capacitors, the other terminals of which are connected, through blocking-capacitors 4I and 4l', to the grids 42, 42' of two push-pull ampliiier-tubes 43, 43'. The cathodes 44 and 44' of the two ampliiier-tubes 43, 43 are connected together at 45, and connected to the oscillator-cathode circuit 21 through a biasing resistor 46. The two ampli-l spective terminals of the primary winding 43 ofv a radio-frequency transformer 4.9. former-primary 48 has a mid-point-tap 50, which is connected to the positive battery-terminal and which is also connected to the screens of the two amplifier-tubes 43, '43. This midu point-tap 58 is also coupled to the two amplifiercathodes 44, 44', through a blocking-capacitor 5|. The output of the radio-,frequency transformer 49 is coupled to one of the conductors of the protected line-section 3 by means of a secondary The transwinding 52 of said radio-frequency transformer.

One terminal of this secondary winding 52 is grounded, as indicated at 53, and a tap 54 is provided to` energize a variometer 55 which is connected, at 55, to a coupling-capacitor 51 whichA is shown as being connected to the phase-C lineconductor. The connecting-point 56 is also connected to ground through a. choke-coil 58.

In addition to the carrier-current transmitter,

which has just been described, I also provide a carrier-current receiver, which is illustrated as' comprising a receiver-tube 59, having a cathode 63, a grid 8|, a. screen B2, and a plate or anode 33. The receiver-cathode 63 is connected, at 84, to a suitable source of negative Ipotential, indicated as being a tap on the potentiometer 3i. l'

The receiver-grid 5I is energized, through a couary-winding 5S of the coupling-transformer G5 is connected to the negative battery-terminal while the other terminal is connected to the receiver-grid 3i. This secondary winding 69 is also shunted by a tuning-capacitor 18.

The receiver-anode 63 is connected to a platecircuit 1l which is, in turn, connected, through a milliammeter MA, to one terminal of a holdingcoil RRH of a receiver-relay RR, the other terminal of the holding-coil being connected to the positive battery-terminal (1,-). The high-irequency component of the receiver-tube current is kept out of the holding-coil RRH by means of a by-pass-capacitor 12, which is connected between the receiver-plate circuit 1I and the receiver-cathode circuit B4. The essential circuit-connections for the .receiver-tube 59 are completed by a connection 13 from the receiverscreen 62 to the positive battery-terminal The receiver-relay RR is illustrated inlFig. 2 as a polarized relay having a tripping-coil RRT for energizing it in a direction to close its two contacts 15 and 1B, this tripping-coil RRT being not as strong as the holding-coil RRI-I, so that the receiver-relay will not respond to the tripping-coil RRT unless the holding-coil RRI-I is substantially deenergized. The two receiver-relay contacts 15 and I6 have a common terminal 11 which constitutes the tripping-circuit of the circuit-breaker 4, for energizing the trip-coil TC throughthe auxiliary breaker-switch 4a and the positive battery-terminal (-l-) The Various relaying-controls exercised by the line-responsive relays can now be described. The contacts of the phase-directional relay DA and the second-zone (or less sensitive) phasefault detector Z2A are utilized to control a re- -laying-circuit '18, the energization of which can be traced, from the negative battery-terminal through the DA contact and the Z2A contact, and thence to the aforesaid relaying-circuit 18. This relaying-circuit 1.8 is utilized for two purposes: in one branch, it is connected to the receiver-relay contact 15, and thence to the tripping-circuit 11; while in another branch, this relaying-circuit 18 energizes an auxiliary phase-fault relay CSP, which is thus energized in response to a phase-fault which is accompanied by an inward direction of line-current iiow, such as will actuate the directional element DA.

A second relaying-circuit 19 is similarly energized in response to ground-faults, in a circuit whichcan be traced from the negative batteryterminal through the Du contact and the 102 through the back-contact of the CSGrelay to the cathode-circuit 2l' of the oscillator-tube 22. The effect of this connection is to make the oscillator-cathode 23 negative, and `thus to start carrier-current transmission. When the negative cathode-connection from the cathode-circuit 27 to the negative battery-terminal through vthe three relay-contacts CSG, CSP and Z3A is broken, carrier-current transmission is prevented, by means of a resistance 82 which is connected between the cathode-circuit 21 andthe positive battery-terminal so that the oscillator-cathode 23 is held at a positive potential, rather than a negative potential, at all times, except when a direct connection is made from the cathode-circuit 27 to the negative source.

The receiver-relay tripping-coil RRT, in series with a resistance 83, is connected across the two serially-connected back-contacts of the auxiliary directional relays CSP and CSG, so that this receiver-relay tripping-coil is normally short-circuited by these CSP and CSG back-contacts.

Connected between the intermediate point 8| and the negative terminal, is the sensitive ground-detector contact 103, which is thus placed in shunt-circuit relation to the two contacts Z3A and CSP, in the carrier-starting control, so that, when there is a ground-fault, the ground-fault relays 103 and CSG take precedence over the phase-fault relays ZSA vand CSP in controlling the transmission of carrier.

I have also shown an other uses control-contact K, connected, at 84, between therelayingbus 8U and the negative battery-terminal for the purpose of initiating carrier-current transmission for testing, telemetering, 'communicaticn, or other purposes. It will thus be noted that the fault-directional contacts CSP and CSG are both in series with the K-contact, in the transmission-controlling circuit, so that, in the event of a line-fault, accompanied by an internal direction, or by a direction accompanied byv a line-current flowing into the protected line-section 3, the carrier-current transmission can be interrupted, at all times, by an actuation. of4 one of the auxiliary directional relays CSP or CSG, as is necessary in the proper operation of the protective apparatus.

In accordance with my invention, I provide an auxiliary contactor-switch CS, or other means responsive to a carrier-starting fault-indication, and 1 have 'also provided the previously men'- tioned push-button PB, and also a resistance 85 which is normally shunted by the push-button PB. The operating-coil of the auxiliary contactor-switch CS is energized from the relayingbus 80, being connected between-said bus and the positive battery-terminal (-f-), so that it is energized, in response to a sensitive phase-faultdetermination, by the relay Z3A, or it may also be energized in response to a sensitive groundfault determination, by the relay 103, if the latter picks up in response to a fault which does not result in thel energization of the CSP relay, the latter circuit being traceable from the negative bus the 103 contact, the conductor 8l, the CSP contact, the relaying-circuit 88, and the CS coil. The CS contactor or relay has a make-contact which is connected in shunt across the push-button PB, and across the resistance 85, so asvto make sure that the resistance 85 is shortcircuited whenever there is a fault on the transmission system.v

In operation, the fault-responsive'part of the equipment operates in the manner which is now energization` of the receiver-relay holding-coil RRH), inlorder` to prevent an'erroneous trippingoperation in the event of a, throughfault, or fault somewhere beyond the other end of the protected line-section 3. It will be understood that the protective equipment will be the same, or similar, at the two ends of the protected line-section, and that the two Vtransmitters 2l will be tuned to the same carrier-current frequency, so that the receivers V5l1andRl=tv at. both ends of the protected line-section will. be energized if either transmitter isfoperating. When a, fault occurs, a sensitive, fault-detector, such as Z3A or 103, first initiates carrier-current transmission. The initiation of carrier-current transmission instantly energizes the receiver-relay holding-coil RRH, and thus prevents the receiver-relay RR from responding to any closing-impulse of its tripping-coil RRT. At either end of the protected line-section, where the fault-current is accompanied by an internal direction, one of the auxiliary directional relays CSP 'or CSG will respond, opening its back-contact, thus interrupting. carrier-current transmission at that end, and simultaneously energizing the receiver-relay trip-coil RRT at that station. If vthe fault-current direction is an into-the-linelooking direction at both ends of the protected section, carrier will be removed from both ends, and;the receiver-relay holding-coils RRH will be deenergized, permitting both receiver-relays RR to respond and complete a tripping-circuit through their contact l5 or 16,.according as the fault isa phasefault or a ground-fault.

In the protective-relay operation of the receiver-tube 59, in accordance With the mode of operation just described, the tube-operates as a saturatedtube, so .that'its plate-current is largely independent of the value of its grid-voltage. The receiver-tube '59 isfurthermore usually protected by means of a voltage-limiting neon glow-tube 86, which is connected across the terminals of the primary winding 61 of the coupling-transformer 65 which energizes the receiver-grid 6|, the function of this glow-tube 86 being to limit the gridvoltage to a certain maximum amount, which is nevertheless enough toV fully saturate the tube, but designed to protect the tube from failure as the result of every excessively large received-signals, such as might be obtained from the transmitter 2| at the same station as the receiver,

In accordance with my present invention, means are provided for, at times, operating the receiver-tube 59 in its non-saturated condition, that is, Awith a grid-voltage which is small enough so that the plate-current of the tube varies approximately in accordance with variations in the grid-voltage. One such non-saturated use of the receiver-relay 59 is in connection with sleet-detection, whereby it is possible to determine the presence or absence of sleet on the protected transmission-line section, by comparing the intensity of the received carrier-current signal with other readings taken at times when there is no sleet.

For the purpose of detecting small changes in the received carrier-current signal, I utilize any suitable desensitizing means in connection with the receiver-tube 59, this meansbeing illustrated in the form of the resistor in series with the supply-circuit to the coupling-transformer 65 which feeds the receiver-grid 6I. The resistance 85 is'normally short-circuited by the normally closed contacts of the push-button PB, so that,

under these conditions, the receiver-grid 6l alwhen either carrier-current transmitter is operating, so that the receiver-tube 59 Will be operating `in its saturated range, in which its plate currentI is a maximum and is not greatly aiected by the magnitude of the carrier-current signal. When it is desired to test for sleet, the receiverdesensitizing push-button PB is depressed, and at the same time the carrier-current starting-control switch K is closed, at the other endof the protected line-section, and the magnitude of the receiver plate-current is determined, as by means of a reading of the milliammeter MA in the platecircuit 1l ofthe receiver-tube 59. i

`Ii a fault should occur on the transmission system, at a time when an operator is testing the line for sleet, byrdesensitizing'the carriercurrent receiver, it is necessary to instantly" restore the intensity of the received carrier-current signal, in order to enable the receiver-tube 59 to deliver suiicient plate-current to adequately energize the receiver-relay holding-coil RRH, so as to prevent an unwanted tripping-operation in the event of a throughfault. To this end, the auX- iliary contactor-switch CS is provided, which closes its make-contact, and re-short-circuits the grid-circuit resistance 85, even though the pushbutton PB might be in its open position at the moment. By making the contacter-switch CS as fast, in its operation, or faster, than the auxiliary directional relays CSP or CSG, it is possible to make sure that the operativeness of the receiverrelay holding-coil RRH is restored, before the receiver-relay trip-coil RRT can be energized in 'response to an operation of one of the auxiliary directional relays CSP or CSG. l

While I have described my invention in a single illustrative form of embodiment, which is at present the preferred form of embodiment, I wish it to be understood that my invention is not limited to this precise form, and I desire that the appended claims shall be accorded the broadest construction consistent with their language.

I claim as my invention:

l. A carrier-current protective relaying system, comprising the combination, with a transmissionline section having circuit-interrupting means to be protectively controlled, of 'protective relayingapparatus including carrier-current transmitting and receiving-means coupled to the line-section, line-fault-responsive relaying-means for controlling both the carrier-current means and the circuit-interrupting means in a manner requiring a predeterminedly strong receipt of carrier to block erroneous circuit-interrupter operations under some fault-conditions involving faults on the transmission system but not in the protected linesection, the carrier-current receiving-means being normally in a sensitive receiving-condition for receiving a strong carrier-signal but operating saturatedly to produce a receiver-current which is approximately limited to said required predeterminedly strong receipt of carrier, other-uses meansfor at' times controlling the carrier-current means in such manner as to desensitize the carrier-current receiving-means so that it will oper` ate substantially unsaturatedly to produce a weakened receiver-current which is approximately proportionate to the strength of thereceived carrier-signal, other-uses means for responding to the magnitude of the weakened receiver-current, and protective-relay-means for giving preferential carrier-current control to the line-faultresponsive relaying-means at all times, including fault-responsive means for restoring the sensitivity of the carrier-current receiving-means so that it will operate saturatedly to provide the required predeterminedly strong receipt of carrier.

2. The invention as dened in claim 1, characterized by said carrier-current receiving-means including a receiver-relay having a trip-coil means and a holding-coil means, the latter being responsive to the receiver-current, and said linefault-responsive relaying-means including means for initiating carrier-current transmission and means for energizing the trip-coil means of the receiver-relay, as well as the means for restoring the sensitivity of the carrier-current receivingmeans, the times of operation being such that the Y carrier-current transmission is initiated and the receiving-means sensitivity is restored at least as soonas the trip-coil means of the receiver-relay is energized.

SHIRLEY L. GOLDSBOROUGH. 

